The present invention relates to the construction of the monitoring device for sensing and controlling the passage of slubbing or fiber roving in the draw frame of a textile spinning machine.
A known drafting machine is provided with a draw frame having at least a set of inlet rollers for receiving the roving or sliver from a source, and a set of exit rollers spaced therefrom, between which the roving is drawn. The exit rollers, feed the drawn material, as thread or yarn to a bobbin or cop on which it is wound. The sets of rollers each comprise a driven lower and a pair of axial spaced (double) upper rollers permitting the drawing of two rovings side by side. The upper rollers are journalled in ranked pairs on a common supporting arm extending in the direction of drawing. Such a machine is disclosed in U.S. Pat. No. 4,450,677 dated May 29, 1984, which also provides means for sensing the proper winding of the drawn thread, including a light source and a photo-light receiving cell mounted at the exit end of the draw frame. A roving clamping device is activated after a break in the exiting thread has occurred, thus, preventing the feeding of additional roving to the draw frame.
In the thread monitoring device shown in U.S. Pat. No. 4,450,677 the light source and the light sensitive cell are arranged on separate components which can be adjusted and locked in positions relative to each other. For operational reasons these parts are situated near to the moving path of the thread emerging from the pair of exit rollers of the draw frame. During operation of the machine it is necessary to perform a great deal of thread-piecing and maintenance work which require a lot of manual activity in the area where the light and light sensitive cells are mounted, and in many instances tools are used. The danger thus exists that the above-mentioned sensitive thread cells are mounted, and in many instances tools are used. The danger thus exists that the above-mentioned sensitive thread monitoring components may suffer damage. If this happens, the most sensible course of action is to replace the damaged component (light source or light-sensitive cell) together with the part holding it with an undamaged component. In the case of the known thread monitoring devices this is accomplished by unscrewing the screw securing the component to the support bar. However, this screw is also the screw retaining the component in the position in which, with the help of an adjustment device, it was initially expertly adjusted in relation to the other functional components of the thread monitoring device and in relation to the moving thread path at the time the device was initially fitted to the machine. Consequently, replacing a damaged component with an undamaged one involves renewed adjustment of the thread monitoring device, requiring a great deal of time and expertise.
It is the object of the present invention to provide the component of the thread monitoring device which holds the light source and the light-sensitive cell such that it is easily installed in precise relationship to one another and to the thread path while permitting the exchange of a damaged component with an undamaged one and maintaining the already adjusted alignment of the parts in relation to one another.
These objects together with other objects and advantages are set forth in the following disclosure of the present invention.